The Misperception of Antidepressants and Mass Shootings

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With new mass shootings in the United States, several ways of reacting to violence are showing themselves. Crying, lamenting, disbelief, anger, fear, depression, confusion. Psychologically, many people need to point a finger at something or someone right away. It’s too painful to wait for more information or to process any complexities.

Of course, sometimes our first simplistic answer is correct. And of course, the shooter is to blame—we can point our finger there with confidence. But what’s behind the shooter’s behavior? There is unlikely to be only a single cause, and law enforcement needs time to gather information (Stalder, 2019). Even weeks and months later, there may still be lingering questions.

It’s not just psychologically difficult to have to wait to blame. For elected representatives, there are also political drawbacks to waiting. After a mass shooting, there is pressure to pass gun-control legislation, and so many Republicans immediately blame anything other than guns (Lutz, 2023). Some Democrats see an opportunity to rally support for their gun-safety measures (Tucker, 2023). Some politicians may downplay any role for the alleged shooter’s ideology if it overlaps in any way with their own or with a political ally’s (Gittleson and Doom, 2019). In politics, putting your answer out there quickly is not just about satisfying a psychological need. It’s also about “setting the narrative.”

Judgment Under Uncertainty and Illusory Correlation

Unfortunately, the emotions and uncertainty surrounding mass shootings, whether psychological or political, increase the likelihood that initial explanations are inaccurate. The reasons for the inaccuracy go beyond the initial scarcity of verified information. Uncertainty can trigger biased thinking processes, particularly according to the seminal work of psychologists Daniel Kahneman and Amon Tversky titled “Judgment Under Uncertainty: Heuristics and Biases” (Tversky and Kahneman, 1974; Kahneman et al., 1982). Heuristics and biases may be efficient and fast, but they contain a great risk of systematic error.

One of those errors falls under “illusory correlation,” which refers to the perception of a relationship between two variables where no relationship, or a much smaller one, exists. Random events that co-occur may naturally seem connected even when they’re not, especially if we already believe that they should be connected.

One of the more surprising examples is the overstated link between arthritis pain and the weather. Many arthritis sufferers swear by it, but the research support has been largely absent, or, at best, mixed with smaller-than-expected effect sizes (Schmerling 2019, 2020). Some react more extremely to weather than others, but there may be a confirmation bias at play whereby individuals cite weather changes during increases in pain but ignore similar weather changes at other times. Redelmeier and Tversky (1996) wrote that “a single day of severe pain and extreme weather might sustain a lifetime of belief in a relation between them.”

The Case of Antidepressants

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So when an extreme event occurs like a mass shooting, and we learn the alleged shooter was taking an antidepressant, or SSRI, some may infer a connection where it doesn’t exist. Rep. Marjorie Taylor Greene and former Fox News host Tucker Carlson have received recent attention for their claims in this regard (Shoaib, 2023). Greene blamed the recent Texas-mall mass shooting on "mental illness, drugs, and evil forces" and said we need to "study SSRI's and other factors that cause mass shootings."

Carlson has cited the “many, many” examples of shooters who were prescribed antidepressants (Carlson, 2022), but these examples constitute less than a fourth of the mass shootings (Hudnall, 2023; Shoaib, 2023). If we’re going to make an argument based on the proportion of mass shootings where something co-occurs, then we should consider guns as well, because they co-occur 100 percent of the time.

Research Findings

In fairness to Greene, she did not contend that SSRIs are the only cause, and there is some research support for her general position. A 2020 large-scale study did show a link between SSRI use and violent crime (Lagerberg et al., 2020). The authors suggested a “biologically plausible explanation” for adolescents in which the SSRI can increase restlessness or agitation which, in combination with the disorder that led to the SSRI prescription in the first place, could result in higher aggression.

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However, the authors acknowledged several caveats. Among them, their biological proposal didn’t pertain to post-adolescent participants; they only knew that participants “purchased” the SSRI and not that they used them; and they could not “infer causality”—the individual’s disorder or any of its environmental correlates could be the reason for the violent crime and not the SSRI itself. The authors concluded, “Given that a vast majority of individuals taking SSRIs will not commit violent crimes, our results should also not be used as reason to withhold SSRI treatment from patients who may benefit from it.”

I can add another observation. Because the preceding conditions and not the SSRI might’ve led to the violent crime, it is possible that if these individuals had never taken the SSRI, they might’ve turned to violent behavior even sooner. Some research suggests that SSRIs can reduce aggression (Butler, 2010; Constantino et al., 1997; Hudnall, 2023) even while the preceding conditions might be pushing the individual toward some violent act that the prescribed SSRI cannot ultimately prevent. And many mass shooters had stopped using their SSRIs before the shooting (Hudnall, 2023).

SSRIs Versus Guns

Unlike antidepressants, the research on guns shows a clear cause-effect connection with aggression, not just because of the physics of guns firing the bullets but also because of the “weapons effect.” Just the visible presence of guns can prime hostile thoughts and increase aggression, though not necessarily to the level of mass shootings (Anderson et al., 1998).

In Sum

Despite the co-occurrence of SSRI use and some mass shootings, experts discount a causal role for SSRIs (Hudnall, 2023; Shoaib, 2023). When people claim a connection, there can sometimes be psychological or political motivations behind it. The best and probably most frustrating advice for how to handle a mass shooting is not to jump to conclusions about the cause.